Restructuring - Schedule of Accrued Restructuring Included in Accrued Expenses and Other Liabilities by Cost Type (Details) - USD ($) $ in Millions	3 Months Ended		15 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020
Restructuring Reserve [Roll Forward]
Balance, beginning	$ 35
Costs charged to expense	23	$ 57	$ 160
Cash payments	(8)
Balance, ending	50		50
Costs charged to expense	23	$ 57	160
Severance and employee-related costs
Restructuring Reserve [Roll Forward]
Balance, beginning	32
Costs charged to expense	23		99
Cash payments	(6)
Balance, ending	49		49
Costs charged to expense	23		99
Facilities and related costs
Restructuring Reserve [Roll Forward]
Balance, beginning	0
Costs charged to expense	0		29
Cash payments	0
Balance, ending	0		0
Costs charged to expense	0		29
Other costs
Restructuring Reserve [Roll Forward]
Balance, beginning	3
Costs charged to expense	0		32
Cash payments	(2)
Balance, ending	1		1
Costs charged to expense	$ 0		$ 32